Abstract:

A method of forming a turbine component that includes a ceramic matrix
composite-ceramic insulation composite with a vapor resistant layer is
disclosed. The method includes providing an inner tool and an outer tool,
wherein the inner and outer tools define a mold for forming a turbine
component. A vapor resistant layer can be applied to the inner tool, and
a ceramic insulation layer can be applied over the vapor resistant layer
in the mold. The vapor resistant layer and the ceramic insulation layer
can be partially fired to form a bisque turbine component, and the outer
tool can be removed. The inner tool can include a transitory material. A
layer of ceramic matrix composite material can be applied to the outside
of the bisque turbine component to form a component, and the component
can be fired to form a turbine component.

Claims:

1. A method of forming a turbine component having a vapor resistant layer,
comprising:providing an inner tool and an outer tool, wherein the inner
and outer tools define a mold for forming a turbine component;applying a
vapor resistant layer to the inner tool;applying a ceramic insulation
layer over the vapor resistant layer in the mold;partially firing the
vapor resistant layer and the ceramic insulation layer to form a bisque
turbine component; andremoving the outer tool.

3. The method of claim 2, further comprising removing the transitory
material and the inner tool.

4. The method of claim 2, further comprising removing the transitory
material and the inner tool after forming the bisque turbine component.

5. The method of claim 1, wherein applying the vapor resistant layer
comprises applying the vapor resistant layer comprising a composition
selected from the group consisting of HfSiO4; ZrSiO4;
Y2Si2O7; Y2O3; ZrO2; HfO2; ZrO2
stabilized by yttria, HfO2 stabilized by yttria, ZrO2/HfO2
stabilized by yttria, yttrium aluminum garnet; Rare Earth (RE) silicates
of the form RE2Si2O7; RE oxides of the form
RE2O3; RE zirconates or hafnates of the form
RE4Zr3O.sub.12 or RE4Hf3O.sub.12; and combinations
thereof, wherein RE is one or more of Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho,
Er, Tm, Yb, and Lu.

6. The method of claim 1, further comprising,applying a layer of ceramic
matrix composite material to the outside of the bisque turbine component
to form a component; andfiring the component.

7. The method of claim 6, further comprising machining the ceramic
insulation layer of the bisque turbine component before applying the
ceramic matrix composite layer.

8. The method of claim 6, wherein providing an inner tool comprises
providing the inner tool comprising a transitory material, and the method
further comprises removing the transitory material and the inner tool.

9. The method of claim 8, further comprising installing a inner machining
tool in the bisque turbine component after the inner tool is removed,
wherein the inner machining tool comprises a second transitory material.

10. The method of claim 9, further comprising machining the ceramic
insulation layer of the bisque turbine component after installing the
inner machining tool and before applying the ceramic matrix composite
layer.

11. The method of claim 10, wherein the transitory material and the second
transitory material are different.

12. The method of claim 10, further comprising removing the second
transitory material and the inner machining tool after machining the
ceramic insulation layer of the bisque turbine component.

13. The method of claim 6, further comprising compacting the ceramic
matrix composite material using a CMC compaction tool.

14. The method of claim 6, wherein the component is a turbine component
selected from the group consisting of transitions, combustor liners,
combustor ring segments, vane shrouds and blade platform covers.

15. The method of claim 1, wherein applying the vapor resistant layer
comprises applying the vapor resistant layer in the form of a viscous
paste, a paint, a tape, a spray, or a combination thereof.

16. The method of claim 1, wherein applying the vapor resistant layer
comprises applying the vapor resistant layer to the inner tool using an
intermediate outer tool, wherein the inner tool and the intermediate
outer tool form a mold for casting the vapor resistant layer.

17. The method of claim 16, further comprising,stabilizing the vapor
resistant layer; andremoving the intermediate outer tool before applying
the ceramic insulation layer.

18. The method of claim 1, further comprising stabilizing the vapor
resistant layer, wherein the vapor resistant layer is stabilized by a
process comprising heating, drying, curing, and combinations thereof.

19. The method of claim 18, wherein the vapor resistant layer is partially
stabilized and diffusion between the vapor resistant layer and the
ceramic insulation layer occurs before or during the partial firing step.

Description:

FIELD OF THE INVENTION

[0001]The present invention is directed generally to a method of forming a
ceramic turbine component having a vapor resistant layer.

BACKGROUND OF THE INVENTION

[0002]The firing temperatures produced in combustion turbine engines
continue to be increased in order to improve the efficiency of the
machines. Turbine engine components that include ceramic matrix composite
(CMC) materials have been developed for applications where the firing
temperatures may exceed the safe operating range for metal components.
U.S. Pat. No. 6,197,424, describes a gas turbine component fabricated
from CMC material and covered by a layer of a dimensionally stable,
abradable, ceramic insulating material, commonly referred to as friable
graded insulation (FGI).

[0003]Several processes have been developed for manufacturing turbine
components from FGI/CMC composite materials. For example, U.S. Pat. No.
7,093,359 discloses a composite structure formed by a CMC-on-insulation
process, and U.S. Pat. No. 7,351,364 discloses a method of manufacturing
a hybrid FGI/CMC structure. These hybrid FGI/CMC components offer great
potential for use in the high temperature environment of a gas turbine
engine.

SUMMARY OF THE INVENTION

[0004]The present invention is directed to a method of manufacturing
ceramic turbine components that include a vapor resistant layer. The
method of forming a turbine component having a vapor resistant layer can
include providing an inner tool and an outer tool, wherein the inner and
outer tools define a mold for forming a turbine component. A vapor
resistant layer can be applied to the inner tool, and a ceramic
insulation layer can be applied over the vapor resistant layer in the
mold. The vapor resistant layer and the ceramic insulation layer can be
partially fired to form a bisque turbine component. The outer tool can
then be removed. The ceramic insulation layer can be a friable graded
insulation.

[0005]The inner tool can include a transitory material. The transitory
material can be removed in order to remove the inner tool. The transitory
material and the inner tool can be removed after the bisque turbine
component is formed.

[0006]The vapor resistant layer can have a composition selected from the
group consisting of HfSiO4; ZrSiO4; Y2Si2O7;
Y2O3; ZrO2; HfO2; ZrO2 stabilized by yttria, RE
or both; HfO2 stabilized by yttria, RE or both; ZrO2/HfO2
stabilized by yttria, RE or both; yttrium aluminum garnet; RE silicates
of the form RE2Si2O7; RE oxides of the form
RE2O3; RE zirconates or hafnates of the form
RE4Zr3O.sub.12 or RE4Hf3O.sub.12; and combinations
thereof, wherein RE is one or more of Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho,
Er, Tm, Yb, and Lu. The vapor resistant layer can be applied in the form
of a viscous paste, a paint, a tape, a spray, or a combination thereof.

[0007]The vapor resistant layer can be applied to the inner tool using an
intermediate outer tool, wherein the inner tool and the intermediate
outer tool form a mold for casting the vapor resistant layer. The vapor
resistant layer can be stabilized and the intermediate outer tool can be
removed before applying the ceramic insulation layer. The vapor resistant
layer can be stabilized by a process comprising heating, drying, curing,
and combinations thereof. The vapor resistant layer can be stabilized,
and diffusion between the vapor resistant layer and the ceramic
insulation layer can occur before or during the partial firing step.

[0008]The method can also include applying a layer of ceramic matrix
composite material to the outside of the bisque turbine component to form
a component and firing the component. The ceramic matrix composite
material can be compacted using a CMC compaction tool. The CMC compacting
step can occur before the firing step. The ceramic insulation layer of
the bisque turbine component can be machined before applying the ceramic
matrix composite layer.

[0009]After the inner tool is removed, an inner machining tool comprising
a second transitory material can be installed in the bisque turbine
component. The ceramic insulation layer of the bisque turbine component
can be machined after installing the inner machining tool and before
applying the ceramic matrix composite layer. The transitory material and
the second transitory material can be different materials. The second
transitory material and the inner machining tool can be removed after
machining the ceramic insulation layer of the bisque turbine component.

[0010]The component formed can be a turbine component selected from the
group consisting of transitions, combustor liners, combustor ring
segments, vane shrouds and blade platform covers.

[0011]These and other embodiments are described in more detail below.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012]The accompanying drawings, which are incorporated in and form a part
of the specification, illustrate embodiments of the presently disclosed
invention and, together with the description, disclose the principles of
the invention.

[0013]FIG. 1 is a perspective view of a cylindrical turbine engine
component formed using the method of the present invention.

[0014]FIG. 2 is a cross-sectional view of the cylindrical turbine engine
component of FIG. 1 taken along section line 2-2.

[0015]FIG. 3 is a cross-sectional view of a mold formed by an inner tool
and an outer tool.

[0016]FIG. 4 is a cross-sectional view of a vapor resistant layer formed
using a mold between an inner tool and an intermediate outer tool.

[0017]FIG. 5 is a cross-sectional view of a vapor resistant layer applied
to an inner tool that includes a transitory material.

[0018]FIG. 6 is a cross-sectional view of a vapor resistant layer and a
ceramic insulating layer formed using a mold between an inner tool and an
outer tool.

[0019]FIG. 7 is a cross-sectional view of a bisque turbine component of
the present invention.

[0020]FIG. 8 is a cross-sectional view of a turbine component formed using
a mold between an inner machining tool and a CMC compaction tool.

[0021]FIG. 9 is a front view of CMC fibers being applied to a bisque
turbine component as part of the CMC application process.

DETAILED DESCRIPTION OF THE INVENTION

[0022]As shown in FIGS. 1 and 2, this invention is directed to an
improved, lower cost hybrid FGI/CMC (friable graded insulation/ceramic
matrix composite) manufacturing process that incorporates a vapor
resistant layer 12 into the manufacturing process for forming a component
10. The process of manufacturing the component can incorporate near net
FGI 14 casting to reduce machining and lower costs, provide a smoother
hot face for improved component aerodynamics, reduce the number of tools
and manufacturing operations, and provide a component 10 with in-situ
manufactured water vapor resistance for natural gas, hydrogen or syngas
fueled and oxyfuel turbines.

[0023]The invention includes a method of forming a turbine component 10
having a vapor resistant layer 12 that can include providing an inner
tool 16 and an outer tool 18, wherein the inner 16 and outer tool 18
define a mold 20 for forming a turbine component, as shown in FIG. 3. A
vapor resistant layer 12 can be applied to the inner tool 16 and a
ceramic insulation layer 14 can be applied over the vapor resistant layer
12 in the mold 20. The vapor resistant layer 12 and the ceramic
insulation layer 14 can be partially fired to form a bisque turbine
component 22. The outer tool 18 can then be removed. The ceramic
insulation layer 14 can be a friable graded insulation.

[0024]As shown in FIG. 3, the inner tool 16 can include a transitory
material 17. The transitory material 17 can be removed in order to remove
the inner tool 16 after the bisque component 22 is formed. As shown in
FIG. 7, the transitory material 17 and the inner tool 16 can be removed
after the bisque turbine component 22 is formed. As used herein, a
"bisque turbine component" is a component that has been partially fired.
For example, where the sintering temperature of the FGI layer 14 is
approximately 1600 degrees Celsius, a bisque FGI layer 14 can be formed
by partially firing the FGI layer 14 at about 1300 degrees Celsius or
less, or about 1200 degrees Celsius or less, or about 1000 degrees
Celsius or less.

[0025]As used herein, a "friable graded insulation" includes coarse-grain
refractory materials useful as ceramic insulation, including insulations
formed from a plurality of hollow oxide-based spheres of various
dimensions, a refractory binder and at least one oxide filler powder,
such as those described in U.S. Pat. No. 6,197,424 by Morrison et al.,
the entirety of which is incorporated herein by reference. As used
herein, "transitory materials" 17 include any material that is thermally
and dimensionally stable enough to support the vapor resistant layer 12,
the ceramic insulating material 14, or both, through a first set of
manufacturing steps, and that can then be removed in a manner that does
not harm the vapor resistant layer 12, such as by melting, vaporizing,
dissolving, leaching, crushing, abrasion, crushing, sanding, oxidizing,
or other appropriate methods.

[0026]In one embodiment, the transitory material 17 may be styrene foam
that can be partially transformed and removed by mechanical abrasion and
light sanding, with complete removal being accomplished by heating.
Because the inner mold 16 contains a transitory material portion 17, it
is possible to form the mold 20 to have a large, complex shape, such as
would be needed for a gas turbine transition duct, while still being able
to remove the inner mold 16 after the vapor resistant layer 12 has
solidified around the inner mold 12. As shown in FIG. 3, the inner mold
12 can consist of a hard, reusable permanent tool 19 with an outer layer
of transitory material 17 of sufficient thickness to allow removal of the
permanent tool 19 after the elimination of the fugitive material portion
17. The reusable tool 19 may be formed of multiple sections to facilitate
removal from complex shapes.

[0027]The vapor resistant layer 12 can be formed from a composition
including, but not limited to, HfSiO4; ZrSiO4;
Y2Si2O7; Y2O3; ZrO2; HfO2; ZrO2
stabilized by yttria, HfO2 stabilized by yttria, ZrO2/HfO2
stabilized by yttria, yttrium aluminum garnet; Rare Earth (RE) silicates
of the form RE2Si2O7; RE oxides of the form
RE2O3; RE zirconates or hafnates of the form
RE4Zr3O.sub.12 or RE4Hf3O.sub.12; and combinations
thereof, wherein RE is one or more of Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho,
Er, Tm, Yb, and Lu. The vapor resistant layer 12 can be applied in the
form of a viscous paste, a paint, a spray, a tape, a combination thereof,
or other appropriate form.

[0028]As shown in FIG. 4, the vapor resistant layer 12 can be applied to
the inner tool 16 using an intermediate outer tool 24, wherein the inner
tool 16 and the intermediate outer tool 24 form a mold for casting the
vapor resistant layer 12. As shown in FIG. 5, the vapor resistant layer
12 can be stabilized, and the intermediate outer tool 24 can be removed
before applying the ceramic insulation layer 14.

[0029]A slurry coating of a composition that is more vapor resistant than
the ceramic insulating material 14 can be applied to an inner tool 16.
The inner tool 16 can define a net shape or near net shape of the exposed
surface of the final turbine component 10. The vapor resistant layer 12
can then be dried, partially fired, or both, so that it may accept the
ceramic insulating material 14 during a subsequent partial firing
process.

[0030]The vapor resistant layer 12 can be applied or cast onto the inner
tool 16. For example, the vapor resistant layer 12 can be applied by a
number of different processes including slurry coating the inner tool 16
surface, custom casting a layer using an intermediate outer tool 24, and
applying a pre-prepared tape layer that can be applied to the inner tool
16, which can serve as a mandrel. In some embodiments, the inner tool 16
can include a transitory material 17 that can be removed by various
methods including oxidation via combustion.

[0031]The vapor resistant layer 12 can be stabilized by a process
comprising heating, drying, curing, and combinations thereof. The vapor
resistant layer 12 can be partially stabilized, and diffusion between the
vapor resistant layer 12 and the ceramic insulation layer 14 can occur
before or during the partial firing step. For example, the vapor
resistant layer 12 can be dried or partially cured before application of
the ceramic insulating material 14. This enables improved diffusion and
bonding between the vapor resistant layer 12 and the ceramic insulating
material 14 during formation of the bisque turbine component 22. Using
the techniques provided herein, it is possible for the vapor resistant
layer 12 to from a hermetic or near hermetic seal over the ceramic
insulating material 14.

[0032]The method can also include applying a layer of ceramic matrix
composite 26 material to the outside of the bisque turbine component 22
to form a component 10 and firing the component 10. The ceramic matrix
composite 26 material can be compacted using a CMC compaction tool 28, as
shown in FIG. 8. The CMC compacting step can occur before the firing or
sintering step. The ceramic insulation layer 14 of the bisque turbine
component 22 can be machined before applying the ceramic matrix composite
layer 26.

[0033]The partial firing of the bisque component 22 can serve at least
three purposes. First, the partial firing can help to stabilize the
bisque component during subsequent processing steps. Second, the bisque
structure 22 has not been fully densified, which can allow for improved
diffusion, both thermal and viscous, of the CMC material 26 into the
ceramic insulating layer 14. Finally, both the CMC 26 and bisque
component 22 are densified during the final firing step, which can help
minimize or prevent undue interfacial stresses from forming between the
CMC 26 and the ceramic insulating material 14. As used herein, the
unmodified term "stabilized" includes fully stabilized, partially
stabilized (i.e. fully or partially sintered/fired), or both.

[0034]After the inner tool 16 has been removed, an inner machining tool 30
comprising a second transitory material 32 can be installed in the bisque
turbine component 22, as shown in FIG. 8. The ceramic insulation layer 14
of the bisque turbine component 22 can be machined after installing the
inner machining tool 30 and before applying the ceramic matrix composite
layer 26. The transitory material 17 and the second transitory material
32 can be different materials. The second transitory material 32 and the
inner machining tool 30 can be removed after machining the ceramic
insulation layer 14 of the bisque turbine component 22.

[0035]The component 10 that is formed can be a turbine component
including, but not limited to, a transition, combustor line, combustor
ring segment, vane shroud and blade platform cover. The present method is
not limited to these components and may be adapted to form other turbine
components as well.

[0036]After the bisque turbine component 22 has been formed, CMC 26 can be
applied to form a turbine composite 10 comprising a hybrid VRL/FGI/CMC
system. For example, the CMC 26 can be applied to the bisque turbine
component 22 using the techniques disclosed in U.S. Pat. Nos. 7,093,359
and 7,351,364, the entireties of which are incorporated herein by
reference.

[0037]Once the bisque turbine component 22 is formed, an inner machining
tool 30 can be used to help support the bisque turbine component 22
during the subsequent machining, firing, or both. The inner machining
tool 30 and the non-transitory portions of the tool disclosed herein can
be manufactured of a refractory material. The inner machining tool 30 can
be manufactured of a material with a coefficient of thermal expansion
similar to that of the turbine component system 10. This can help prevent
excessive stresses from being generated between layers of the turbine
component 10.

[0038]Following removal of the outer tool 18, the thickness of the layer
of ceramic insulating material 14 can be reduced using a mechanical
process such as by machining the insulating material 14 in its partially
or fully stabilized state with the inner tool 16 in place. The outer
surface of the insulating material 14 can be prepared for receiving a
ceramic matrix composite layer 26 while the inner tool 16 remains in
place to provide support for the VRL 12 and the ceramic insulating
material 14 during the CMC application process. The CMC application
process can include the application of any CMC precursor form including,
but not limited to, fiber tows, fabric strips or fabric sheets that can
be applied by either hand or machine processes to conform to the bisque
turbine component 22 before final firing step. The CMC material 26 can be
any known oxide or non-oxide composite. It may be desired to at least
partially cure the VRL 12 and ceramic insulating material 14 before
removing the inner tool 16.

[0039]If the transitory material is transformed by heat, the curing
temperature during processes before removal of the inner tool 16 can be
less than a transformation temperature of the transitory material portion
17 of inner tool 16. Thus, the mechanical support provided by the inner
tool 16 is maintained. Consecutive layers of the CMC 14 material may be
applied to build rigidity and strength into the turbine component 10.

[0040]The bisque turbine component 22 can provide adequate mechanical
support for the machining step, the application of the CMC 26 material,
or both, thereby allowing the inner tool 12 to be removed. Alternatively,
the inner tool 12 can remain in place through the entire processing of
the turbine component 10. At an appropriate point in the manufacturing
process, the transitory material portion 17 of inner tool 16 can be
transformed, the inner tool 12 removed, and the turbine component 10
processed to its final configuration.

[0041]If the ceramic insulating material 14 is not machinable in its green
state, or if the transitory material 17 is not stable at a desired firing
temperature, the transitory material 17 and inner mold 12 can be removed
before the firing step, and an inner machining mold 30 may be installed
before the firing step or as a support before a subsequent mechanical
processing step, such as machining or applying a layer of CMC material
26. The transitory material portions 17, 32 of the first inner mold 16
and the inner machining mold 30, respectively, do not necessarily have to
be the same material. For example, the transitory material 32 used in the
inner machining tool 30 can be specially selected to be compatible with
chemicals used in a machining fluid or at temperatures required for an
intermediate or final sintering step.

[0042]In instances where the CMC layer 26 is being applied to a
cylindrical bisque turbine component 22, the outside surface of the
bisque turbine component 22 can serve as a mold for the subsequent
deposition of a CMC layer. For example, the CMC layer 26 can be formed by
winding of a plurality of layers of ceramic fibers 27 around the bisque
turbine component 22. A refractory bonding agent may be applied to the
exterior of the bisque turbine component 22 before the addition of the
ceramic fibers 27. FIG. 9 illustrates the composite component at a stage
when only a portion of the layers of ceramic fibers 27 have been wound
around the bisque turbine component 22 and before the CMC layer 26 is
subjected to autoclave curing. The ceramic fibers 27 can be wound dry and
followed by a matrix infiltration step, deposited as part of a wet
lay-up, or deposited as a dry fabric (including greater than 2D fabrics)
followed by matrix infiltration. Any of these methods can be used with an
applied pressure, such as that created by a CMC compaction tool 28, to
consolidate the CMC layer 26 with processes and equipment known in the
art. Fiber and matrix materials used for the CMC layer 26 may be oxide or
non-oxide ceramic materials, including, but not limited to, mullite,
alumina, aluminosilicate, silicon carbide, or silicon nitride. The CMC
layer 26 can fully conform to the dimensions of the outside of the bisque
turbine component 22 and the matrix material can at least partially
infiltrate into pores of the ceramic insulating layer 14 of the bisque
turbine component 22. FIG. 2 illustrates a cross-sectional view of a
portion of the finished turbine component 10 showing the seamless
interfaces between the VRL 12 and ceramic insulating material 14 and
between the ceramic insulating material 14 and the CMC layer 26.

[0043]The tools disclosed herein can be made of a porous material. The use
of tools with different pore sizes accelerated or inhibit heating,
cooling and moisture removal during the process disclosed herein. Thus,
the porosity of the tools is a variable that can be used to manipulate
the properties of the turbine components 10 formed using the methods
disclosed herein.

[0044]The foregoing is provided for purposes of illustrating, explaining,
and describing embodiments of this invention. Modifications and
adaptations to these embodiments will be apparent to those skilled in the
art and may be made without departing from the scope or spirit of this
invention.